1. Field
The present work relates generally to digital communication systems, and more specifically to the implementation of spectrum selection in the public broadband.
2. Background
The Federal Communications Commission (FCC) has ruled that television (TV) white space will be allowed to be used for public broadband after the United States has abandoned analog television broadcasting in 2009. The term “white space” refers to portions of the television spectrum that are located between ultra high frequency (UHF) television channels. The white space portions of the television spectrum were originally set up as a buffer zone to protect the analog television channels from stray signals and other interference. Now that analog television technology has been abandoned in favor of digital television technology, the white space spectrum is no longer needed to provide analog television buffer zones and is available for other uses.
The FCC decision has made two widely separated spectrum frequency groups available for public broadband akin to Wi-Fi and its variants. These spectrum groups comprise 700 MHz (TV white space), 5 GHz and 2.5 GHz. Considering that these frequency groups are widely separated, the most appropriate spectrum must be selected at given points in time. Sub-optimal efficiency results in low spectral efficiency and creates inter-device incompatibility.
Traditional wireless protocols that are currently in use implement Channel Impulse Response (CIR) based spectrum allocation. Fixed spectral allocation is also known. Neither method is efficient where frequency groups are widely separated. CIR based allocation may allocate a lower frequency group all of the time because lower frequency channels will have good CIR for both shorter and longer distance links. However, higher frequency channels do not have good CIR for longer ranges/distances.
If lower frequency channels are reserved for longer ranges and higher frequency channels are reserved for shorter ranges, higher spectral efficiency can be achieved.
There is therefore a need in the art for spectrum selection based on range and distance.